1. Field of the Invention
The present invention relates to a recording medium such as BD-ROM (Blu-ray Disc ROM), which includes copy protection indicating information and an apparatus and methods for forming, recording, reproducing, and restricting reproduction of illegally duplicated recording media.
2. Description of the Related Art
Recently, standardization of a new high-density optical disc, a rewritable Blu-ray disc (BD-RE: Blu-ray Disc-Rewritable), have been under development where large quantities of high quality video and audio data can be recorded. Once the standard of a BD-RE has been established, products adopting the new optical discs are expected to be commercially available in the near future.
As illustrated in FIG. 1, a BD-RE has an inner hole; clamping area, transition area, BCA (Burst Cutting Area) area, and lead-in area, located in sequential order along radial direction. A data area and lead-out area reside in the center and outermost annulus of the disc, respectively.
The lead-in area is partitioned into a first guard (Guard 1) area, PIC (Permanent Information & Control data) area, a second guard (Guard 2) area, Info 2 area, OPC (Optimum Power Calibration) area, etc. The first guard area and PIC area are pre-recorded areas, whereas the remaining lead-in areas, data area, and lead-out area correspond to rewritable areas which can be overwritten with new data.
General information of a disc which needs to be permanently preserved may be recorded in the PIC area, which can be encoded in wobbled grooves of a track by HFM (High Frequency Modulation) method. HFM Grooves may be modulated in the radial direction with a rather high bandwidth signal, to create a data channel for replicated information with sufficient capacity and data rate. As shown in FIG. 2, encoding data into wobbled groove can be performed by bi-phase modulation and thus recording.
In this modulation method, a bit with value 0 may be represented by a transition at the start of the bit cell and a bit with value 1 may be represented by a transition at the start and in the middle of the bit cell. The modulated bits may be recorded on the disc by a deviation of the groove from its average centerline as indicated in FIG. 2. The length of each bit cell may be 36 T, where T corresponds to the length of a channel bit in the rewritable data areas.
Along with the development of a BD-RE, has been the development of a corresponding read-only disc, a read-only Blu-ray disc (hereinafter, referred to as ‘BD-ROM’). As shown in FIG. 3, the BD-ROM disc may include an inner area, clamping area, transition area, information area, and rim area.
The main data of an audio/video (A/V) stream recorded in a data zone within an information area can be recorded with encryption with copy protection information (CPI) to prevent unauthorized copy.
Various disc information (DI) about the disc, such as the type of a disc, may be recorded in the PIC area within the information area. When encrypted main data are recorded in the data zone, copy protection information (CPI) for decryption can also be recorded in PIC area.
When an optical disc apparatus playing a recording medium performs initial servo operations in accordance with the insertion of a disc, copy protection information (CPI) recorded in the PIC area is detected. If main data recorded in a pre-recorded data area is found to be encrypted, the main data is output after decryption using the copy protection information.
Even when copy protection information is not recorded in the PIC area because the contents recorded in data area of a BD-ROM are not encrypted, an optical disc apparatus performing initial servo operations still performs a series of operations to detect copy protection information in the PIC area under the assumption that encryption has been applied to the contents. Such a preliminary operation can cause a delay in the playback of actual data. Also, if any data is recorded on the rewritable disk, i.e., BD-RE, or recordable disk, i.e., BD-WO and its data is copy protected, a similar problem exists when the data is reproduced.
Further, if copy protection information is not detected, it cannot be determined whether there is no copy protection information initially because the disc is an illegal medium, or there is no copy protection information because the disc is a legal and copy-free medium.